Part of Zodiac was added later?

[Koen G]

I think that all of VM was written by a man.

By now it is generally accepted that the VM text was written by several scribes, thanks to the work of Lisa Fagin Davis. See here: You are not allowed to view links. Register or Login to view.
Maybe this is what you heard? These scribes are not separated per section though. For example You are not allowed to view links. Register or Login to view. and You are not allowed to view links. Register or Login to view. are not written by the same person. 

The conclusion is that we know for sure that several people worked on the VM, but we have no reason to assume that parts of the manuscript were added later.